In the production of spherolytic or nodular cast iron, i.e. cast iron containing spheroidal or globular graphite, the cast iron melt may be treated with substances, known in the art, for inducing the formation of spheroidal graphite. Such treatment can be carried out in a ladle between the blast furnace or other furnace in which the cast iron melt is formed and the location at which the melt is to be cast into molds.
Tiltable ladles have been provided for this purpose in the past (see, for example, German patent application DE-AS No. 22 16 796) in which the ladle is formed like a tiltable converter so as to swing about a transverse axis, i.e. an axis perpendicular to the longitudinal axis of the elongated ladle which may have a charging and tapping opening at one end, i.e. the top, when the ladle is in an erect state.
At the opposite end or bottom, the ladle is provided with a chamber into which the substance capable of inducing formation of spheroidal graphite is introduced.
This chamber can be charged with the inducing substance from the exterior and communicates with the melt-receiving compartment of the ladle via openings in the wall therebetween.
These openings permit penetration of the melt into the chamber and passage of vapors of the inducing substance upwardly into the melt when the ladle is in an erect position.
The mouth of the converter, into which the molten iron is charged and from which the molten iron is discharged or tapped, can be closed with a cover.
In the horizontal position of the converter, the melt is charged into the latter in such manner that it does not come into contact with the contents of the aforementioned chamber. When the ladle is swung into its erect position, however, molten metal passes through the opening into the chamber and vapors of the substance capable of inducing spheroidal graphite formation pass upwardly to treat the melt.
The charging of such vessels with the melt and the inducing substance is time-consuming and labor intensive, and the maintenance and labor operations are extensive. In addition, since the converter cannot be used effectively as a transport or casting vessel, the treated melt must be transferred to a transport ladle and cast from the latter into the molds.
Another treating unit is described in German Open Application DE-OS No. 25 14 490 and has the configuration of a cylindrical vessel rotatable about the axis of the cylinder, i.e. a horizontal axis.
This ladle has a filling and tapping opening and is partitioned internally by a grate into a melt-receiving chamber and a chamber which can be charged from the exterior with the substance capable of inducing the formation of spheroidal graphite.
Even this ladle has not been found to be effective in all cases.
For example, for some casting purposes it is necessary to provide an intermediate receptacle or ladle below the treatment drum. The technological defects of this system include high maintenance and replacement costs for the grate enclosures.